Information flow within the nervous system requires the perpetuation of ionic gradients along neurons. In many neurons, effective and efficient perpetuation of such gradients along axons requires electrical insulation. Myelin, a lipid-rich, dielectric substance that ensheathes axons, serves this insulating function. The nervous system contains high levels of myelin, which is especially enriched where many myelinated axons are bundled together, such as in tracts of the spinal cord and spinal nerve roots, nerves in the peripheral nervous system, and fiber tracts in the brain, collectively called “white matter” (as opposed to “grey matter”). Because non-nervous system tissue lacks myelin, the presence of myelin can distinguish peripheral nerve tissue from other tissue types, the spinal cord and spinal nerve roots from non-nervous elements of the vertebral column, and white matter from grey matter.
The ability to qualitatively or quantitatively visualize myelin, either in vivo or in vitro, confers upon researchers and clinicians important diagnostic and treatment tools. For example, the ability to visually identify peripheral nerves during surgery assists surgeons in avoiding cutting or damaging nerves. Additionally, in vivo myelin imaging of the spinal cord assists clinicians in the diagnosis and treatment of spinal cord pathology, such as nerve compression or herniated discs as well as myelin-associated neuropathies, such as multiple sclerosis which results in damage to myelin within the central or peripheral nervous system. The ability to measure amounts of myelination in vivo in patients with such conditions would aid clinicians and researchers in diagnosing and prognosing myelin-associated neuropathies.
Additionally, myelin detection is useful to preclinical and basic neuroscience researchers. Myelinated nerves and fiber tracts serve as useful landmarks in anatomical studies. Furthermore, the formation of myelin sheaths is an important step in the generation and functional stability of new neurons, so the availability of myelin markers help researchers study such processes. Myelin-labeling methodologies are also useful in the development of numerous therapies, neural stem cell research, and putative animal models of myelin-associated neuropathies.